If you can't write Keyczar bindings for Ruby, maybe cryptography is a little ambitious for you too.
Note: Bouncy Castle is not a recommended high-level crypto library. More grevious errors are committed in the name of Bouncy Castle than almost anything but OpenSSL.
Of course I have the technical ability to write C bindings (or whatever it is) for $arbitrary_library. Your whole thesis, however, is "crypto is hard, so don't try to do it yourself", so I asked for suggestions on how not to do it myself.
And I only mentioned "Bouncy Castle" because it was suggested in the article.
Note: Bouncy Castle is not a recommended high-level crypto library. More grevious errors are committed in the name of Bouncy Castle than almost anything but OpenSSL.